(1) Field of the Invention
The present invention relates to an electrode wearable and more particularly to an electrode wearable suitable for the acquisition of multi-lead ECG including 12-or-more-lead ECG with various features that enhance the use and performance of the electrode wearable. The present invention further relates to a method of taking biopotential measurements.
(2) Description of Related Art
An accepted standard in electrocardiogram (ECG) recordings of subjects is the “12-lead” ECG, or in pediatric subjects or in certain adults undergoing specialized testing, the “13-, 14-, or 15-lead” ECG. In the context of this disclosure and in the ECG field generally, “lead” refers to a voltage difference between two electrodes or between an electrode and a “central terminal” such as Wilson's, rather than to a lead wire or its corresponding electrode. Thus a traditional 12-lead ECG does not actually require 12 electrodes (or 12 lead wires), but usually only 10 electrodes: six standard “precordial” electrodes placed on the chest (termed, from left to right across the chest, V1, V2, V3, V4, V5, and V6) and four standard “limb” electrodes placed on or near each of the four appendages (termed RA, LA, RL, and LL, for the right and left arms and legs, respectively). Similarly, a common type of pediatric ECG uses all of the above electrodes but also adds so-called V3R and/or V4R electrodes (directed more rightward) and/or a V7 electrode (directed more extremely to the left and approaching the back). While the traditional placement of the appendage electrodes is distally, as far as possible away from the heart, modified electrode placement schemes which have relocated the distal electrodes to proximal positions on the torso have also gained clinical acceptance, e.g., the Mason-Likar placement. Another modified electrode placement known as the Lund placement system has been shown to yield measurements that are in better agreement with the traditional distal ECG electrode placement scheme than those measurements recorded with the Mason-Likar method (see, e.g., Welinder et al., “Differences in QRS Axis Measurements, Classification of Inferior Myocardial Infarction, and Noise Tolerance for 12-Lead Electrocardiograms Acquired From Monitoring Electrode Positions Compared to Standard Locations”, Am J Cardiol 2010;106:581-586).
A traditional ECG setup requires extensive time, training and expertise to set up and record high-quality signals suitable for analysis and/or diagnosis of disease or defect. Conventional gel-type electrodes require skin preparation at the electrode sites involving cleaning and abrasion to remove dead skin cells at the epidermis that increase electrode impedance and lower signal quality. Electrodes themselves must be properly cleaned and gelled prior to use, or pre-fabricated disposable electrodes must be used, which contribute to cost. Electrodes must be placed at the proper sites on the skin and not misplaced at sites too distant from clinically accepted placements, otherwise, the variability of placements can result in incomparable recordings which can increase the complexity of analysis and result in misdiagnosis (see, e.g., Jowett et al., “Modified electrode placement must be recorded when performing 12-lead electrocardiograms,” Postgrad Med J 2005;81:122-125). Lead wires must be kept trim and orderly, so as to reduce motion artifact and noise and eliminate the possibility of accidental dislocation, and care must be taken to connect lead wires correctly at both ends, so as not to produce a faulty recording. Altogether, the knowledge, patience, and care that must be taken to record quality ECG recordings using traditional equipment and methods is beyond that possessed by the average ECG subject, making self-administration impractical, and rapid administration impossible even with the assistance of an expert technician or clinician to aid in the recording setup.
Various wearables have been developed to solve some of the above problems. U.S. Pat. No. 4,608,987 to Miller depicts a vest to which lead wires attach externally on the chest. U.S. Design Pat. No. 313,652 to Lavine illustrates a vest with electrodes and lead wires embedded in it, along with “arms” of unascertainable function. U.S. Pat. No. 5,224,479 teaches a 12-lead ECG diagnostic pad with belts for attachment at the shoulders. U.S. Pat. Nos. 6,205,346 and 6,341,229 to Akiva describe an apron holding ECG and other sensors; the device of the former disclosure requires bracelets. U.S. Pat. No. 6,408,200 to Takashina shows an electrode-embedded apron which can be placed over a supine subject. U.S. Pat. No. 6,516,289 to David teaches a glove or glove-and-sling apparatus which requires the subject to hold his left arm across his chest. U.S. patent application Ser. No. 10/937,539 of Wolff et al. briefly discusses a form-fitting sensor harness applied by means of an adhesive backing. U.S. Pat. No. 7,266,405 to Alroy et al. teaches a foldable electrode assembly designed to be portable and easily used by the unaided subject. U.S. patent application Ser. No. 11/713,334 shows a harness that aids in electrode placement on the chest. U.S. patent application Ser. No. 11/576,765 of Montplaisir shows a system of three straps, one for the chest and one for each arm. U.S. patent application Ser. No. 11/719, 338 of Gazit and Ser. No. 11/749,253 of Kurzweil et al. describe belt-type electrode harnesses with straps. U.S. patent application Ser. No. 12/464,878 of Grossman describes an ECG shirt comprising a elastic shirt having holes at various sites for electrode placement and elastic straps for fastening electrodes and lead wires, and having printed upon the shirt various labels and instructions to aid in placement or for training purposes. The teachings of all of the foregoing publications are expressly incorporated by references; many of the foregoing publications further list other references, each of which is also herein incorporated by reference.
Despite all the various contemplations by others, not all of the problems of quickly and accurately acquiring a resting 12-or-more-lead ECG have been solved by existing designs. Many of the designs use proximal electrode placements of the limb electrodes, whereas more distal placement is preferable; those that use more distal placement resort to additional apparatus (such as bracelets, belts, or gloves, or adhesives) or disadvantageous methods of use (such as requiring the subject to forcefully squeeze his or her arms against his or her chest or against electrodes placed in or near the armpits) in order to record signals from more distal electrode sites. Many of the designs require gels or adhesives to be placed on the body, which can dry out, become uncomfortable, and result in poor recordings because of increased electrode impedance or failure of electrode attachment. Many of the previous devices are susceptible to myoelectric noise or are uncomfortable to wear, even for short periods, although ideally an apparatus for collecting resting multi-lead ECG is comfortable to wear over a period of several minutes or longer. Many of them are too complicated to be donned or doffed unaided. Many of them involve excessive pieces or components which are less conveniently stored or transported.
In view of the foregoing drawbacks, it is an object of the present invention to provide a electrode wearable for resting multi-lead ECG, including for 12-or-more-lead ECG, that comes in one piece and preferably has no more than one point of connection/disconnection around the body, so that it can be easily, quickly, and comfortably donned and resized, providing the proper electrode placement without possibility of incorrect placement, without the use of adhesives on the body, and without requiring substantial muscular exertion on the part of the subject during ECG recording which can taint the ECG signal with myoelectric noise. It is further the object of the present invention to provide an electrode wearable than can be used and re-used without cleaning or preparation of electrodes or skin sites so as to provide an “always-ready, instant-on” electrode wearable. It is further the object of the present invention to provide an electrode harness or vest which records the appropriate limb electrode signals from placement sites that are more distal than those of other electrode harnesses and vests without requiring a multiple-piece apparatus that may be susceptible to misplacement or misuse by the untrained individual and in any case would require additional time and hassle to don and doff. Finally, it is the object of the present invention to have an electrode wearable containing dry electrodes.